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May
9, 2008: Any Trekkies out there? Remember the tricorder?
Dr. McCoy and Mr. Spock both carried them, and they came in
mighty handy exploring "strange new worlds ...where no
one has gone before."
On
the International Space Station, astronauts are carrying an
experimental device that looks strikingly similar: LOCAD-PTS,
short for Lab-On-a-Chip Application Development Portable Test
System. This handheld biological lab is the first step along
the path to developing something akin to Dr. McCoy's medical
tricorder.
![see caption](images/tricorder/suni_med.jpg)
Above:
Astronaut Suni Williams (with flowing "microgravity locks"
of hair) uses LOCAD-PTS onboard the International Space Station.
"LOCAD
is like that tricorder in that it is portable, rapid, and
detects a biochemical molecule," says Heather Morris,
LOCAD scientist from NASA's Marshall Space Flight Center,
and an admitted Star Trek fan. But while tricorders could
do almost anything from checking vital signs to finding alien
life, LOCAD is a little more specialized: "LOCAD is specifically
designed to detect and identify microbes on space station
surfaces."
It
is a fact of life that wherever humans go, microbes follow.
Biologists estimate that every human body has at least a trillion
hitchhiking microbes, accounting for as much as 2% of a person's
total mass. Most live in harmony with native human cells;
others can make you sick.
LOCAD
keeps track of these tiny lifeforms.
Here's
how it works: An ISS crewmember uses a dry swab to take samples
of surfaces where microbes might be lurking. Flushing sterile
water through the swab converts the sample to liquid form,
and the astronaut puts a few drops into the LOCAD. What's
in the sample? The system gives its answer less than 15 minutes
later. The whole easy procedure is done on location. Nothing
has to be sent back to a lab on Earth, which would take time
and introduce the possibility of contamination en route.
"It's
important to monitor bacteria on the space station so we can
find the best way to keep them under control," says Morris,
who adds this curiosity: "LOCAD can't yet distinguish
between live and dead bacteria." So no one can cry out,
it's dead, Jim! "We're working to add this capability
in the future."
Right:
Heather Morris works on LOCAD technology in her laboratory
at the Marshall Space Flight Center.
In
addition to detecting Gram-negative1 bacteria like
E. coli and salmonella, the latest LOCAD cartridges just sent
up to station aboard shuttle mission STS-123 can alert the
crew to fungi. Since fungi actually decomposed some electronics
on the Russian Space Station MIR, they have become unwelcome
"house guests." LOCAD can detect low concentrations
of a common fungal compound; this allows LOCAD to find fungi
on surfaces before the fungi have a chance to multiply.
By
the end of the year, yet another cartridge will be available
for the space station. This one will detect the presence of
Gram-positive bacteria such as staphylococcus and streptococcus.
"Ultimately
we want to provide cartridges for all kinds of micro-organisms
and chemical compounds," says Morris. "We'd even
like to be able to use our system to figure out what 'bug'
an astronaut has if he or she becomes ill."
Lisa
Monaco, LOCAD scientist, adds her vision of the future: "What
we are developing at MSFC has use not only on the ISS, but
also on lunar missions, long duration stays on other planets,
and most certainly here on Earth."
In
the years ahead, as space voyages become longer and longer,
it will be even more imperative to have ways of checking astronauts'
health and monitoring electronics. For the record, no astronaut
has ever become seriously ill on any space mission. However,
the scientists point out that if an astronaut did ever get
sick, it would take too much time to send a sample back to
Earth, have it tested, and receive a long-distance answer.
With next-generation LOCAD technologies, detection and diagnosis
would be quick, easy, and on the spot.
Dr.
McCoy, here we come.
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Author: Dauna Coulter
| Editor:
Dr. Tony Phillips | Credit: Science@NASA
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LOCAD-PTS
--home page
Gram
staining (or Gram's method) is an empirical method of
differentiating bacterial species into two large groups
(Gram-positive and Gram-negative) based on the chemical
and physical properties of their cell walls.
The
method is named after its inventor, the Danish scientist
Hans Christian Gram (1853 – 1938), who developed the
technique in 1884 to discriminate between pneumococci
and Klebsiella pneumoniae bacteria.
1Gram-negative
bacteria are those bacteria that do not
retain crystal violet dye in the Gram staining protocol
Gram-positive bacteria will retain the crystal violet
dye when washed in a decolorizing solution. In a Gram
stain test, a counterstain (commonly safranin) is added
after the crystal violet, coloring all Gram-negative
bacteria a red or pink color. The test itself is useful
in classifying two distinct types of bacteria based
on structural differences in their cell walls.
Many
species of Gram-negative bacteria are pathogenic, meaning
they can cause disease in a host organism. This pathogenic
capability is usually associated with certain components
of Gram-negative cell walls, in particular the lipopolysaccharide
(also known as LPS or endotoxin) layer. In humans, LPS
triggers an innate immune response characterized by cytokine
production and immune system activation. Inflammation
is a common result of cytokine production, which can also
produce host toxicity.
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